Catchment boundaries and size

Hi,

does anyone know if it's possible to define catchment boundaries (and thus calculate size) in GE or GE Pro? and no, I don't want to do that by hand, this is painstaking.
thanks

I was a party to a discussion of this issue several years ago in the old GEC. I'd hunt it up for you and send you a link, but the consensus was that it couldn't be done, at least from Google Earth elevation data.

As I recall, I had worked out the basic logic (not very elegant) but enough so I was convinced that a computer program could be written that would map drainage basins. (Don't ask me now what I had in mind. I can't tell you. All I can say is that I was convinced at the time that it was possible.)

Here are some problems:

• The elevation database used in Google Earth is pretty much a black box; that is to say, as far as I know, nothing has ever been published about how it is structured.
  
• Even if you could reverse engineer the program, the data is proprietary, and it seems doubtful that one could ever get permission to use it.
• The data base is designed to render the imagery in 3D, but it doesn't seem to be of very high resolution. (My hunch is that it's a series of connected elevation points, but the spaces between the points may be higher or lower, and are probably not the slopes that are rendered.)
  
• Heaven knows how the new 3D Cities data base may complicate the problem.

If I were bent on mapping catchment areas by computer, I'd give up on Google Earth, and look around to see who may have created elevation data bases, and whether or not they were available, affordable, and suitable for my purposes.

If I wanted to produce a map on Google Earth, I start with a topographic map and a colored pencil, scan the result, overlay it, and then trace the map with the polygon tool.  The area of the polygon should be available in Google Earth Pro (now free).

Let us know if you find a better method.

Edit: There is no indication of whether or not you have read this reply.  The previous discussion I referred to (which doesn't shed any significantly different light on the question) may be found >>HERE<< in the old GEC.

Hi,
You can delineate catchments and map drainage networks accurately by using either SRTM or ASTER digital elevation models. You will need to work with a plugin called TAUDEM by David Tarboton of the Utah State University in ArcMap. TAUDEM can be downloaded from: hydrology.usu.edu/taudem/taudem5/downloads.html.
SRTM and ASTER DEMs can be downloaded from: earthexplorer.usgs.gov.

Here's an example of the Goriganga River in the Himalaya: 

Attachments:

goriganga_subbasins.KMZ (56.89 KB)